Robert Weiss had been told repeatedly his rare, blistering skin disease was untreatable when he found his way to a Boston area specialist known in medical circles for an alternative treatment.

In Dr. Abdul Razzaque Ahmed, Weiss found the miracle he'd been looking for.

His disease went into remission and he no longer had to suffer the severe side effects of long-term use of steroids, the common treatment for his illness.

It wasn't until years later - when he was contacted by federal investigators - that Weiss learned Ahmed had been deceiving Medicare to get treatment for him and other patients with pemphigoid, a disease that was not covered by Medicare at the time.

"I certainly don't believe he should have done what he did, but I'm grateful to him," said Weiss, 89, of Orono, Maine, a retired physician.

"I can tell you that he saved my life, in the sense that I would have died if I had to stay on [steroids] - not from the pemphigoid, but from the treatment itself," Weiss said.

Federal prosecutors acknowledged yesterday that Ahmed was helping patients even as he broke the law.

Ahmed pleaded guilty to a single count of obstruction and agreed to surrender $2.9 million in assets.

In exchange, prosecutors agreed not to pursue 14 other more serious charges - including healthcare fraud - against him, and said they would not seek prison time when he is sentenced Feb. 4. Ahmed declined to comment yesterday.

Authorities had painted a far different picture of Ahmed when he was indicted two years ago, depicting him as a greedy businessman looking to squeeze as much money as possible out of Medicare, the federally subsidized health insurance program for the elderly and people with disabilities.

Prosecutors say he duped Medicare by submitting fake dual diagnoses for 24 patients so he could collect reimbursements for intravenous immunoglobulin treatments, which cost between $10,000 and $12,000 per month.

Ahmed, 59, of Brookline, was indicted on 15 counts of healthcare fraud, money laundering, mail fraud, and obstruction for allegedly collecting $5.4 million in Medicare reimbursements by mixing blood samples of patients with a severe, life-threatening skin disease called pemphigus vulgaris with samples from patients with pemphigoid, a less-serious disease.

Yet to his patients, Ahmed was something of a modern-day Robin Hood, getting them expensive treatments they would otherwise not have been able to afford.

"I was shocked that he had falsified the diagnosis without telling me," said Weiss, who retired in 1986 as dean of the School of Public Health at Columbia University in New York.

Ahmed's attorney, Richard Egbert, said Ahmed treated patients from all over the world who were referred to him by other physicians because conventional therapies were no longer working and had caused harsh complications.

"He gave this treatment to people for the purest of reasons, to alleviate their suffering and save their lives," Egbert said.